Cathode-ray tube



p ,1 J. DE GIER ETAL CATHCDE-RAY TUBE Filed Jan. 28, 1963 United States Patent 3,340,358 CATHODE-RAY TUBE Johannes de Gier, Willem Fokko Nienhuis, and Floris de Boer, Emmasingel, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Jan. 28, 1963, Ser. No. 254,231 Claims priority, application Netherlands, Jan. 29, 1962, 274,116 6 Claims. (Cl. 1787.82)

Our invention relates to glass cathode-ray tubes the glass bulb of which is surrounded in part by an envelope which also serves, at least in part, as a frame for the display surface. More particularly, the invention relates to envelopes for cathode ray tubes comprising at least two annular parts, one annular part also serving as a frame for the display surface and one or more other annular parts of the envelope surrounding at least part of the cone of the tube.

It is known to surround a glass bulb of a cathode-ray tube by an envelope comprising two annular metallic parts, one part of which surrounds the cone of the tube and the other part of which constitutes a frame or mask for the display surface; The space between the envelope and the glass bulb is filled, at least in part, with fibrous elastic material, such as felt or rubber. Such envelopes serve in the first place as a protection against electrical and/or magnetic fields, but also provide a certain protection for the viewer in case of implosion since the fragments, instead of flying about, are intercepted by the envelope. However, the risk of implosion itself is not reduced by such envelopes. In another known embodiment the sealed edge between the window and the cone of the bulb is surrounded by a clamping 'band, while a cement layer may be provided, if desired, between the band and the glass. In this case the risk of implosion is greatly reduced since a crack no longer extends further under the clamping band, but drops at this area or bends over. The bulb then slowly leaks full of air. However, the provisions of a clamping band in the form of an envelope as above described is often impossible since the envelope has to be matched to the state of the bulb and the mechanical provision of clamping stress, for example, by means of pull-bolts, which then gives rise to an irregular distribution of forces.

A further disadvantage of the metal envelopes above described is that the part constituting the frame for the display surface is apt to be touched by the viewer.

In fact, when using such envelopes, it is desirable to omit the protective glass plate in front of the display surface. Since the metal envelope cannot be insulated lest it receives uncontrolled charges, the envelope must be connected to the chassis of the device. In apparatus utilizing a large number of electron tubes, the tubes are usually powered in series, so that the chassis is connected to one pole of the power supply. The chassis may thus have a definite potential with respect to ground, dependent upon the position in which the plug is inserted into the socket, so that it is extremely dangerous to touch the metal frame.

Itis a principal object of our invention to provide a cathode-ray tube for display purposes which is safer for the viewer and in which the danger of implosion is greatly reduced.

A further object of our invention is the provision of a protective guard for a cathode-ray tube in which metal protective parts are inaccessible to the viewer thus assuring greater safety to the viewer.

A still further object of our invention is the provision of a protective guard for a cathode-ray tube which sub- Patented Sept. 5, 1967 stantially reduces the risk of implosion and yet is simple to fabricate.

These and further objects of our invention will appear as the specification progresses.

In accordance with the invention an annular part of an envelope surrounding a cathode-ray tube and serving as a frame for the display surface is made from a hard insulating material which may be armored, if desired, while the space between the glass bulb and the envelope is filled with a non-elastic, coherent mass, preferably hard, which is introduced into said space in a castable or moldable state. The envelope preferably comprises a plurality of annular parts, one part of which serves as a frame for the display surface.

The ring serving as a frame is preferably made from a hard synthetic material, such as synthetic resin or a hard plastic, which may contain glass or metal fibres or textures or in which a metallic band may be provided.

The filling mass is preferably a material which may be poured into the space in the molten state and, after solidification, constitutes a non-elastic coherent mass of sufiicient hardness. Very suitable filling masses are: sulfur, horn material or'resin and certain kinds of hard asphalt. It is also possible to provide the filling mass as a hydraulically-hardenable suspension, such as gypsum, (Portland cement) concrete or mortar. If desired, use may be made of material which hardens to form a porous, hard mass, provided it has sufiicient resistivity to deformation after hardening. Synthetic material which hardens by the action of a hardening agent is also very suitable.

It is known per se to manufacture an envelope from two parts, in which the annular part serving as a mask for the display surface is of a material differing from that of the other part of the envelope. However, in this connection it is emphatically mentioned that such a mask must consist of elastic material, for example rubber..The filler specified for embedding the parts of the envelope is also an elastic material, for example, rubber. Consequently, this known design cannot reduce the risk of impolsion.

The invention will now be described with reference to the accompanying drawing, in which:

FIG. 1 shows one embodiment of a cathode-ray tube according to the invention;

FIG. 2 is a sectional view of part of another embodiment; and

FIG. 2a is an enlarged view of a corner of the envelope shown in FIG. 2.

In FIG. 1 the cone of the glass bulb is indicated by 1 and the viewing screen by 2. The cone 1 is surrounded by an annular part 3, in this example metallic, of an envelope, while an annular part 4, which also serves as a frame for the display surface 2, is made of a hard insulating material, preferably a synthetic resin, which may be armored, if desired. The ring 3 has a flange 5 and the ring 4 has a flange 6 molded thereto. The flanges 5 and 6 are provided with apertures and connected together by means of rivets 7 after the parts 3 and 4 have been placed around the cathode-ray tube which is otherwise already fully completed. The dimensions of the parts 3 and 4 are such that these parts and the glass bulb 1, 2 remain separated by a gap which is filled by casting or pressing with a hardenable material 8. A very suitable material is a hard kind of asphalt or mastic, or horn material from cows horns or horses-hoofs which is poured in the molten state into protuberances 9. The bulb and the envelope are slightly heated, if necessary, for example, up to about 50 C., so that the mass 8 does not solidify too quickly and can fill the gap-shaped space completely. It is also possible previously to cover the annular parts 3 and/or 4 with a layer of a paste-like filler mass and, subsequently, pressing these parts on the bulb so that the space between the envelope and the bulb is completely filled by the plastic mass which is then allowed to harden.

In FIG. 2 the ring 4 is provided with an armor in the form of an embedded metal band as shown in greater detail in FIG. 2a. Instead of utilizing a solid band, use may be made of a band of metal gauze or a texture of glass fibres. The ring 4 in this case preferably consists of synthetic material, such as a polyester or a synthetic T65111- Since no metal parts can be touched from the front of the tube, it is not objectionable if the ring or rings 3, which may be of metal, if desired, acquire a potential relative to earth. Although the ring 3 may alternatively consist of hard insulating material, it is in general desirable to make this ring from metal since it may then be active as a capacitor electrode and as an electrical and, if desired, magnetic shield.

If the filler 8 is sulfur, which may be poured in the molten state between the bulb and the envelope, it is desirable for the edge of the filled space to be coated afterwards with a thin varnish layer 10, since otherwise silvered conductors or silver contacts in the apparatus are apt to be chemically attacked.

Although the envelope 3, 4 does not exert any appreciable pressure on the glass of the bulb, it has been found that, due to the use of the hard filler, sufficient resistance is created as soon as the glass tends to make way, for example due to the occurrence of a crack. Such a crack does not substantially extend farther below the filler so that implosion no longer can occur in practice.

The insulating layer of the ring 4 in FIG. 2 has a thickness such. that it is impossible to touch the metal armor 11, for example, by scratching with a sharp object. Such armor may contact, if desired, through a flange or lug fully embedded in insulating material, with the rivets 7 so that charging by induction is avoided. In fact, such charge could give rise to interference due to additional deflection of the cathode-ray. The flanges 5, 6 may also serve to harden the tube in the cabinet of the apparatus.

The filler 8 may, if desired, be gypsum or concrete (Portland cement) mixed, if desired, with sand (mortar) and be poured as an aqueous suspension between the bulb and the envelope. However, the filler may alternatively be hardenable mixtures of other materials. Thus, a mixture of heated oxide and glycerin is also usable. Loose non-coherent materials, such as sand, are unsuitable, as well as filler masses which are elastic. However, such materials may be added to the mass, if desired, as fillers.

Although only a few embodiments have been described, still further embodiments are possible within the scope of the invention. A necessary condition always is that the annular parts of the envelope, as well as the filling mass, shall consist of materials which are non-elastic and harden sufficiently and that the part of the envelope which serves as a frame for the display surface, except for any armor, consist of a hard, non-elastic insulating material. If desired, this ring may be of ceramic material. In fact, a thin insulating surface layer, for example of varnish, may readily be scratched through by a sharp object so that contact with the metal is possible.

Tolerance differences in the dimensions of the bulb and the ring are neutralized by the space between the bulb and the envelope and hence 'by the thickness of the filler layer.

Thus, while we have described our invention in connection with specific embodiments and applications thereof, other modifications will be apparent to those skilled in the art Without departing from the spirit and scope of the invention as defined in the appended claims.

What we claim is:

1. A cathode-ray tube comprising a transparent window portion and an adjoining cone portion, an envelope spaced from and surrounding a portion of the cone portion of the tube and having a portion forming a frame for the transparent window portion, said latter portion of said envelope being constituted of a hard insulating synthetic resin, and a non-elastic, coherent mass of horn material occupying the space between the envelope and the portions of the tube surrounded thereby.

2. A cathode-ray tube comprising a transparent window portion and an adjoining cone portion, an envelope spaced from and surrounding a portion of the cone portion of the tube and having a portion forming a frame for the transparent window portion, said latter portion of said envelope being constituted of a hard insulating synthetic resin, and a non-elastic, coherent mass of hardened asphalt occupying the space between the envelope and the portions of the tube surrounded thereby.

3. A cathode-ray tube comprising a transparent window portion and an adjoining cone portion, an envelope spaced from and surrounding a portion of the cone portion of the tube and having a portion forming a frame for the transparent window portion, said latter portion of said envelope being constituted of a hard insulating synthetic resin, and a non-elastic, coherent mass of sulfur occupying the space between the envelope and the portions of the tube surrounded thereby.

4. A cathode-ray tube as claimed in claim 3, in which a metal band is embedded in the hard insulating synthetic resin to provide an armor in the frame. 5. A cathode-ray tube comprising a transparent window portion and an adjoining cone portion, an envelope spaced from and surrounding a portion of the cone portion of the tube and having a portion forming a frame for the transparent window portion, said latter portion of said envelope being constituted of a hard insulating synthetic resin, and a non-elastic, coherent mass of hardened concrete occupying the space between the envelope and the portions of the tube surrounded thereby.

6. A cathode-ray tube comprising a transparent window portion and an adjoining cone portion, an envelope spaced fromand surrounding a portion of the cone portion of the tube and having a portion forming a frame for the transparent window of said envelope being constituted of a hard insulating synthetic resin, and a non-elastic, coherent mass of hardened gypsum occupying the space between the envelope and the portions of the tube surrounded thereby.

References Cited UNITED STATES PATENTS 1,641,403 9/1927 Van Derhoef 156-307 1,981,141 11/1937 Caprio 156-307 2,756,892 7/1956 Bleuze 220-2.1 2,785,820 3/1957 Vincent et al. 220-21 3,007,833 11/1961 Jackman 264-261 3,097,061 '7/1963 Woelk 264-261 3,206,056 9/1965 Stel 178-7.82 3,310,194 3/1967 Bradu l78-7.82

JOHN W. CALDWELL, Acting Primary Examiner.

DAVID G. REDINBAUGH, T. E. CORIDON,

Examiners.

I. A. ORSINO, M. L, RICE, Assistant Examiners,

portion, said latter portion 

3. A CATHODE-RAY TUBE COMPRISING A TRANSPARENT WINDOW PORTION AND AN ADJOINING CONE PORTION, AN ENVELOPE SPACED FROM AND SURROUNDING A PORTION OF THE CONE PORTION OF THE TUBE AND HAVING A PORTION FORMING A FRAME FOR THE TRANSPARENT WINDOW PORTION, SAID LATTER PORTION OF SAID ENVELOPE BEING CONSTITUTED OF A HARD INSULATING SYNTHETIC RESIN, AND A NON-ELASTIC, COHERENT MASS OF SULFUR 